On the binary helium star DY Centauri: Chemical composition and evolutionary state
Abstract
DY Cen has shown a steady fading of its visual light by about 1 magnitude in the last 40 years suggesting a secular increase in its effective temperature. We have conducted non-LTE and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 years. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of an He white dwarf with a C-O white dwarf. Thus, DY Cen by chemical composition appears to be also a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.
Cite
@article{arxiv.1408.3798,
title = {On the binary helium star DY Centauri: Chemical composition and evolutionary state},
author = {Gajendra Pandey and N. Kameswara Rao and C. Simon Jeffery and David L. Lambert},
journal= {arXiv preprint arXiv:1408.3798},
year = {2015}
}
Comments
Accepted to ApJ with 8 Figures and 5 Tables